IP Fast Reroute , LFA (Loop Free Alternate) , Remote LFA and in general recovery and protection discussion. In this post, I will share the discussion with one of my slack group member, Driss Jabbar. He is a CCDE and highly skilled network engineer and also author of some posts in this website. You can contact him on Linkedin.

I share this post with his permission.

I asked in the group whether anyone deployed EIGRP FRR (I don’t mean EIGRP Feasible Successor, EIGRP Fast Reroute feature). Driss replied that He deployed IP Fast Reroute for his OSPF network. We talked about his deployment, specifically from the protection,restoration point of view. Hope this real life experience help you in someway.

Orhan Ergun

Hello guys, anyone deployed EIGRP FRR in production ?

Driss Jabbar

I did for ospf

Not for eigrp

Orhan Ergun

for production or in the lab Driss ?

Driss Jabbar

Production

Orhan Ergun

still working ?

Driss Jabbar

What do you mean?

Orhan Ergun

any problem with it ?

Driss Jabbar

Yes

I’am using it for a small mpls service provider

Orhan Ergun

lfa ?

Driss Jabbar

Remote lfa

To cover all kind of failure

Orhan Ergun

so for their topology, coverage is 100%

Driss Jabbar

Yes

Orhan Ergun

per link or per prefix

Driss Jabbar

Per prefix as i have only loopback interfaces

[2:42]

In my routing table

[2:42]

Thanks to suppress prefix

Orhan Ergun [2:43 PM]

prefix suppression you mean ?

Driss Jabbar [2:43 PM]

Exactly

Orhan Ergun [2:43 PM]

how many prefixes approximately you suprress with it

[2:44]

so, routers and the links per router etc

Driss Jabbar [2:45 PM]

We have 2 core routeurs (P) and about 20 PE

Orhan Ergun [2:46 PM]

not much from the scalability aspect but providrd cleaner routing table

[2:46]

why remote lfa ? Didnt regular LFA cover all the failure scenarios ?

Driss Jabbar [2:46 PM]

each PE is connected to both P,so in reality i have no need for remote lfa everywhere

[2:47]

But in a place where i have a circle topology

[2:47]

I have activate it

Orhan Ergun [2:47 PM]

in a ring , LFA creates microloop

[2:47]

and you had to find a PQ node

[2:48]

now, in case of failure, link or node , did you do the test ?

Driss Jabbar [3:26 PM]

back ?

Orhan Ergun [3:26 PM]

yes i am here too

Driss Jabbar [3:26 PM]

ok

[3:26]

so i was saying that the majority of our PE were connected to both P router

[3:27]

so we see all other PE loopbacks from two side

Orhan Ergun [3:27 PM]

where you have a ring topology then

Driss Jabbar [3:28 PM]

in a place where we don’t have control on the fiber links

[3:29]

and the customer has bought the more economic topology (ring) from another fiber provider

[3:29]

and on that place i ve used remote-LFA

[3:30]

in the other places the frr is based only on ECMP

Orhan Ergun [3:31 PM]

Between your PEs and the Ps, are you utilizing LAG or ECMPs ?

Driss Jabbar [3:31 PM]

ECMP

Orhan Ergun [3:31 PM]

you answered already

[3:31]

🙂

Driss Jabbar [3:31 PM]

🙂

Orhan Ergun [3:31 PM]

i am typing from the phone

Driss Jabbar [3:31 PM]

fast as always 🙂

Orhan Ergun [3:32 PM]

but if you are doing ECMP, in case of failure, are you seeing any performance benefit with IP FRR ?

Driss Jabbar [3:34 PM]

i think ECMP handle FRR well,because you have both routes in your FIB and the reroute was very fast in my test

[3:34]

so i decided to reduce configuration complexity when i could

Orhan Ergun [3:35 PM]

yes thats what I mean. Do you need IP FRR, in your case LFA , while you already have ECMP

Driss Jabbar [3:35 PM]

you dont need it

[3:36]

IP FRR should be used in special cases and i did in my ring topology.

Orhan Ergun [3:36 PM]

okay

[3:36]

what about this

Driss Jabbar [3:37 PM]

i could let IP FRR in all my network but i always prefer to make it simple as much as i can

[3:37]

for me and for the support team

Orhan Ergun [3:38 PM]

you said it is MPLS network, probably for transport LSP signalling you are using LDP, did you consider to run RSVP- TE , so you could have MPLS TE FRR , rather than IP FRR

Driss Jabbar [3:39 PM]

why i have to activate an extra protocol (RSVP) if i can treat FRR with only ECMP

[3:39]

?

[3:40]

keep it simple is my best solution

Orhan Ergun [3:40 PM]

thats okay, MPLS TE FRR would be an option in case your topology is not covered 100% for all failures and you are looking 100% coverage.

Driss Jabbar [3:41 PM]

That’s right

Orhan Ergun [3:41 PM]

But in your case, topology is simple and is covered by IP FRR without introducing additional control plane

[3:41]

are you running Multicast on your core network ?

Driss Jabbar [3:43 PM]

my the network we are supporting is a special service provider who deliver only L2 services for others service providers like in france like orange,SFR,COLT….etc

[3:44]

so we are delivering only L2 services

Orhan Ergun [3:44 PM]

okay , multicast us transperent to your network

Driss Jabbar [3:44 PM]

exactly

Orhan Ergun [3:45 PM]

you are not providing Internet access or L3 MPLS VPNs

[3:45]

you are not providing residential service as well right

[3:45]

none of these

Driss Jabbar [3:46 PM]

we are working only with service providers delivering them connexions to them customers

Orhan Ergun [3:46 PM]

i would ask if you have BGP FRR , since would be an option as you have an IGP FRR

Driss Jabbar [3:47 PM]

it depends right

[3:49]

if it’s IBGP, what’s matter is the next hop gateway,if it’s reachable from BGP point of view everything is ok

[3:49]

and this next hop is handled all the time by IGP protocols so i will keep using IGP FRR for IBGP

Orhan Ergun [3:50 PM]

sure. the problem is not only that

[3:50]

if you have a multiple BGP next hop for the same prefix, hoe quickly you will start using the second next hop.i vase primary one fails

[3:50]

BGP PIC Edge

[3:51]

and if you dont wanna wait BGP Control plane to converge, you wanna change the BGP next hop for all affected prefixes as quickly as possible

Driss Jabbar [3:51 PM]

it depends of your design and your architecture

[3:52]

right

Orhan Ergun [3:52 PM]

IGP FRR will help for the first case which you described , it is also called as BGP PIC Core

[3:52]

anyine here runs BGP PIC in production ?

Driss Jabbar [3:53 PM]

as long as you have more than one route in your FIB table you will be fine with FRR

Orhan Ergun [3:53 PM]

sure , if uou have IBGP multipath

[3:54]

but you know that, multipath is not enabled by default in BGP as in the case with IGP

Driss Jabbar [3:54 PM]

founding the best solution denpend to the constraint you face

[3:54]

sure i know

[3:55]

and you can use this option if you don’t have RR in the middle otherwise BGP add path will be a good choice

[3:55]

shadow RR i think

Orhan Ergun [3:55 PM]

what about L2 service

[3:55]

you said you are providing L2 service to the other Providers

Driss Jabbar [3:55 PM]

yes

Orhan Ergun [3:55 PM]

what type of service you provide

Driss Jabbar [3:56 PM]

99% is P2P

[3:56]

and 1% VPLS

Orhan Ergun [3:57 PM]

okay, as we discuss about protection , are you providing fast protection for them ?